How to read the graphs

Understanding wave monitoring graphs effectively involves an understanding of the specific conditions in the area you are interested in. Keep in mind that wave conditions can change rapidly, so always stay informed and exercise caution when engaging in ocean-based activities.

To understand the wave conditions, wave period is often considered alongside wave height (Hs) and wave direction as part of a complete wave analysis.

Wave height graph

• Wave height is measured from the crest (the top of a wave) to the following wave trough (the bottom of a wave) and is measured in metres.
• The vertical axis (y-axis) displays the height measurement of the wave, and the horizontal axis (x-axis) displays the time measurement.
• By default, the graph is set to display the previous three days of wave heights measured by the wave buoys.
• The time scale on the y-axis can be reduced by zooming in on the graph.
• The green line represents the significant wave height (Hs). This is defined as the average height of the highest one-third of waves in a given wave record. It is a statistical measure and does not represent the height of every individual wave but is typically what you would say the average wave heights are if you were to observe them from the beach.
• The blue line is the maximum wave height (Hmax) and specifically refers to the single highest wave observed within a given wave record.
• Higher wave heights can indicate more challenging and potentially hazardous conditions.

Wave period graph

• The red line is wave period, or peak period (Tp) measurements on the horizontal axis (x-axis).
• It represents the time it takes, measured in seconds, for one wave to pass a fixed point (zero up crossings).
• The longer wave periods generally indicate more organized and less choppy conditions. Short periods may result in choppier seas.

Wave direction graph

• Wave direction is typically measured in degrees clockwise from true north, with zero degrees representing waves coming from the north, 90 degrees from the east, 180 degrees from the south, and 270 degrees from the west.
• Wave direction is crucial for understanding how waves will impact your location or activity.

Wave spectrum graph

• The wave spectrum graphs show the distribution of wave energy and period over three days.
• Ocean wave spectrums can vary greatly depending on multiple factors such as wind speed, wind duration, fetch (the distance over which wind blows in one direction), and the presence of swells.
• They make it easy to see if there’s a single, double (bi-modal) or more, dominant frequencies. If there’s more than one dominant wave frequency the waves are usually more unpredictable or variable than if there’s just one dominant wave frequency.